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Avalanche Forecast

Archived

Nov 22nd, 2012–Nov 23rd, 2012

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Little Yoho.

Another system Friday afternoon bringing wind and some snow will bump up the hazard, depending on it's intensity.  Lot's of snow available for transport, expect slab development and naturals to occur tomorrow afternoon.

Weather Forecast

Friday afternoon another system bringing moderate SW wind and snow forecast range from 5-20 cm. This will bump up the hazard tomorrow. Clearer weather Saturday and cooler temps to follow Sat night.

Snowpack Summary

30-50 cm of storm snow at tree-line along the continental divide.  Very little wind effect as of yet...  Easy-moderate shears at storm snow interface and mod shears down 60 cm on Nov 6 crust.

Avalanche Summary

In a flight from Banff to Kootenay, only a few size 1-2 soft slabs were noted, 20-60 cm thick and not propagating far. They released late in yesterdays storm.  There was one notable full depth release on glacial ice on Monarch pk, NE aspect,  2800 m.

Confidence

Intensity of incoming weather systems is uncertain

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.